I took it, and examined it.

“This isn’t mine,” I said. “Where did you find it?”

“Just there, sir,” and he pointed to the ground beside the car.

When I looked at the flask again, I noticed that the tiny shield in the middle was engraved. The engraving was a cipher, which, on scrutinising closely, I made out to be the letters “D.P.” intertwined.

I unscrewed the stopper and smelt the contents. The smell, though peculiar, was not wholly unfamiliar. Still, for the moment I could not classify it.

“Didn’t you drop it, sir?”

“No.”

“Then perhaps I had better take it,” and he held out his hand.

“No, I’ll keep it—you needn’t be anxious,” I said. “I have been staying here, and probably it belongs to somebody in the house, or to somebody who has called.”

I fumbled in my pocket and produced two half-crowns, which at once allayed any conscientious squeamishness afflicting the driver at the thought of handing over his treasure-trove to a stranger.